Field of the Disclosure
The present disclosure generally relates to a sheet detecting device and an image forming apparatus.
Description of the Related Art
Typically, copiers, printers, facsimiles, image reading devices, various finishers, etc. are provided with a sheet detecting device for detecting the passage of a sheet when a sheet, serving as a recording medium, is conveyed.
Examples of a typically used sheet detecting device include a detecting unit that uses a flag which is moved by being pressed by a sheet and a sensor for detecting the flag.
The sheet detecting device that uses the flag is formed of a detection flag, an urging spring, a sensor, a holder for holding these parts, etc. The detection flag is urged in a predetermined direction by the urging spring and is stationed at a standby position so as to cross a sheet conveyance path. When the leading end of a sheet reaches the detection flag, the sheet starts to tilt the detection flag, and, when the detection flag has tilted by a predetermined amount, the sensor detects the tilting of the detection flag. Thereafter, when the trailing end of the sheet has passed through the detection flag, the detection flag returns to the standby position by the urging force of the urging spring.
By detecting the passage of the sheet with the sheet detecting device in the above-described manner, the image forming apparatus can use the detection result as a criterion for various control operations and can detect sheet jamming, double feeding, etc.
In recent years, there has been a demand for even higher throughput of image forming apparatuses, and therefore, a reduction in the space between the trailing end of the preceding sheet and the leading end of the succeeding sheet (hereinbelow, “sheet interval”) is required.
According to the configuration disclosed in Japanese Patent Laid-Open No. 2003-252483, by disposing a detection flag coaxially with a conveyance roller, the rotational angle of the detection flag is reduced, making it possible to detect a small sheet interval.
According to the configuration disclosed in Japanese Patent Laid-Open No. 2012-144350, by making the rotational center of a detection flag changeable, the time for the detection flag to return to the initial position is reduced, making it possible to detect a small sheet interval.